Find definite integrals for the expressions listed as the elements of a matrix

Question

Kobye 2013-6-27

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/80465-find-definite-integrals-for-the-expressions-listed-as-the-elements-of-a-matrix

I have a matrix populated with symbolic expressions in 2 variables. I would like to carry out a definite surface integral of each expression and keep the results in the same matrix format. A dummy code below:

%Clear variables and cmd window
clear;
clc;
%Define symbolic variables
syms x y;
K_unintegrated = syms(zeros(2));
%Populate K_unintegrated matrix with expressions of 2 variables
K_unintegrated(1,1) = x^2;
K_unintegrated(1,2) = x*y;
K_unintegrated(2,1) = y*x;
K_unintegrated(2,2) = y^2;
%Display K_unintegrated matrix
K_unintegrated
%Attempt surface integral of each expression in the matrix (should
%hopefully give a fully numeric matrix)
K=int(int(K_unintegrated,x=0..2),y=0..2)

I get the following error:

Error: File: example.m Line: 20 Column: 27 The expression to the left of the equals sign is not a valid target for an assignment.

The Mathworks site gives the following info:

http://www.mathworks.com/help/symbolic/int.html

Find indefinite integrals for the expressions listed as the elements of a matrix: syms x t z alpha = sym('alpha'); int([exp(t), exp(alpha*t)]) The result is: ans = [ exp(t), exp(alpha*t)/alpha]

This is very much what I would like to do, except I want to evaluate the definite integral of each matrix element.

How can I achieve this in the most efficient way possible?